The Psalterium Sinaiticum is a 209-folio Glagolitic Old Church Slavonic canon manuscript, the earliest Slavic psalter, dated to the 11th century. The manuscript was found in the monastery of Saint Catherine, Mount Sinai, after which it was named and where it remains to this day.
The major part of the psalter (177 folios) was discovered in 1850 by the Russian archimandrite Porfirij Uspensky, and additional 32 folios turned up in 1968.
It was published by L. Geitler (Psalterium. Glagolski spomenik manastria Siani brda; Zagreb 1883), S.N. Severjanov (Sinajskaja psaltyr'. Glagoličeskij pamjatnik XI veka. Prigotovil k pečati Sergej Sever'janov; Saint Petersburg 1922, transcribed to Cyrillic; reprinted in Graz in 1954) and by Moshe Altbauer in 1971, in a facsimile reproduction (Sinajski psaltir, glagolski rakopis od XI. vek od manastirot Sv. Katerina na Sinaj, MANU, Skopje 1971). The manuscript is also extensively discussed with facsimile reproductions in Ioannis C. Tarnanidis: The Slavonic Manuscripts Discovered in 1975 at. St. Catherine's Monastery on Mount Siani (Thessaloniki 1988).
Paleographic and linguistic analysis shows that the writing of some letters is very inconsistent. Especially inconsistent is the writing of yers and nasal vowels, and very obvious is the tendency of the vocalization of jers and the omission of epenthetic l.